Reverse

Reverse an array.

Installation

$ npm install compute-reverse

For use in the browser, use browserify.

Usage

var reverse = require( 'compute-reverse' );

reverse( arr[, options] )

Reverses an array.

var arr = [ 1, 2, 3, 4 ];

var out = reverse( arr );
// returns [ 4, 3, 2, 1 ]

By default, the input array is mutated. To return a new array, set the copy option to true.

var arr = [ 1, 2, 3, 4 ];

var out = reverse( arr, {
	'copy': true
});
// returns [ 4, 3, 2, 1 ];

console.log( arr === out );
// returns false

Examples

var reverse = require( 'compute-reverse' );

var arr = new Array( 100 );
for ( var i = 0; i < arr.length; i++ ) {
	arr[ i ] = i;
}
reverse( arr );

console.log( JSON.stringify( arr ) );

To run the example code from the top-level application directory,

$ node ./examples/index.js

Notes

According to ECMA specification 262, when implementing the native array.reverse() method, one must check whether array elements are defined before determining how to swap elements. If one element is a hole, only the non-hole value is assigned to a temporary value before being assigned to a new position in the array. The element's original position is then deleted. See the V8 (Node.js) implementation for an example.

If we eliminate the hole checks and additional temporary variables, we can streamline the algorithm for performance gains. See jsPerf for benchmarks.

Tests

Unit

Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:

$ make test

All new feature development should have corresponding unit tests to validate correct functionality.

Test Coverage

This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:

$ make test-cov

Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,

$ make view-cov

License

MIT license.

Copyright

Copyright © 2014-2015. Athan Reines.